Glucose-6-phosphate dehydrogenase in rat hepatic stellate cells: an ultrastructural enzyme-cytochemical study

Glucose-6-phosphate dehydrogenase (G6PD) is the key enzyme of the pentose phosphate pathway in carbohydrate metabolism. This enzyme plays an important role in various cell functions, including cell proliferation, lipid/retinol metabolism, etc. Although marked cell proliferation and retinol metabolism take place in hepatic stellate cells (HSCs), it has not been determined whether cytochemically detectable G6PD is present in HSCs. The distribution pattern of G6PD within these cells, if it is present, is also unknown. The purpose of this study was to investigate the subcellular localization of G6PD in rat HSCs using a newly developed enzyme-cytochemistry (copper-ferrocyanide) method. Electron-dense precipitates indicating G6PD activity were clearly visible in the cytoplasm and on the cytosolic side of the endoplasmic reticulum of HSCs. The cytochemical controls ensured specific detection of the enzyme activity. HSCs possessed enzyme-cytochemically detectable G6PD activity. This enzyme may play a role in normal liver biology and liver disease pathophysiology, by supplying HSCs with NADPH and ribose-5-phosphate as a substance/substrate/co-factor for cell proliferation, oxidoreductase enzymes, and retinol metabolism, respectively.